This should interest the SONOS developers. Submit a series of diagnostics. First, prior to building the Group, next after building the Group, then a couple along the way after the Room drifts out of sync. Now you’ll need to attract SONOS’s attention. This is usually done by contacting phone support. Sometimes a moderator will refer a customer to appropriate staff based on posts on here, but don’t count on it.

i think that the cause is some sort of communication issue. The first unit used to build the Group becomes the Group “Coordinator” and all group music traffic flows through this unit. In a stereo pair the left unit is the pair’s Coordinator. 

Are your units wired or wireless?

The design intent is for the units to share some synchronizing data and gently adjust the synchronization from time to time. This is to allow for lost and delayed packets that are part of normal network operation. If you are perceptive and patient enough, you can perceive the adjustments as a very subtle shift in the stereo image. For some reason your rogue pair is not receiving or ignoring this data.

i think that the developers would be interested in this case, but reporting it will require some of your time. If you don’t want to commit to this, I suggest that you factory reset (only) the misbehaving pair. Factory reset will destroy diagnostic data that could have been used to discover the root cause. After the factory reset you’ll need to re “Bond” the pair. 

Thanks @buzz 

Sonos (the company) is currently a little overdrawn on their goodwill account with me at the moment so I think I’ll try the factory reset you suggest.

Thanks for your very helpful response.

Take care to “add” the Factory Reset units to an existing system. Don’t start a new system.

If you do/have reset them, it may be worth testing before you re-pair them, add them as single device(s) to group and try to reproduce.

@IanJShaw

Have you manually assigned your drifting Zone to a specific Deco access point and have you got Mesh Technology on or off for the Sonos speakers, in your Deco app? The reason I ask is whether the speakers (or the whole Zone) is fluctuating in terms of the access point it is connected to - ie. if Mesh Technology is on and it continually seeks a better signal and switches to another access point, a regular fraction of a second shift in AP change could add up to cause drift. Maybe?

Hi @Rhonny 

Thanks for taking the time to suggest this.

I’m afraid I wouldn’t have the first idea how to start doing any of this.

I count myself as reasonably technically competent.  All my Sonos players have reserved IP addresses on the router, for example (the Decos are all in Access Point mode).  But a quick glance at the Deco app doesn’t offer anything that looks immediately obvious to start addressing this.  Also (and this may or may not be relevant), all of the Sonos players just show up in the app as clients named “Sonos”.  I suspect, if I have to do any client-level configuration I’ll need to match MAC addresses to player names and…. well, that once again feels like Sonos outsourcing unfinished development work to me.

Your suggestion is not wasted though.  If I find myself with enough time to start researching how to do this I’ll definitely explore it.  Every day’s a learning day, after all!

Thanks again for your reply.

Open a browser on a laptop/PC go to play.sonos.com, click the cog top right. about my system will display the MAC address of all your Sonos devices.

I assume in your Deco App you can rename devices or add description, you can then give more meaningful names as per the about my system based on MAC address.

In the Deco app (if it has the same layout as mine), if you tap on a device in the list, on the screen that comes up should be a Mesh Technology toggle switch to allow a device to either 1) move seamlessly between the Deco access points (if toggled on), or 2) to remain fixed to one access point (if toggled off).

On that same screen is Connection Preference where you can select the specific Deco access point that you want the device to connect to - usually the closest access point to it.

So in short, you can ensure a Sonos speaker connects to a certain access point and remains fixed to it. This might not solve your problem, but specifying the access point does no harm for a device like a speaker that doesn’t move around the house.

Great, thanks @Rhonny 

Just taken a look and yes, those options are there in mine too.  Something to while away some down-time between clients I think.

And also, this is yet another reminder for me that this community adds so much to the experience of being a Sonos owner.  I’ll avoid commenting on whether it should be necessary or not.  The fact that it is, and you guys are there to help is a very positive experience!

@Rhonny 

Thanks again.  I am cautiously optimistic that this has solved the problem.

After the slightly annoying job of assigning meaningful names to each of my Sonos players in the Deco App I then went through and assigned them all to fixed access points.  Since then I’ve noticed:

 - the misbehaving zone is now much more controllable and doesn’t seem to be losing sync (may be early days yet...)

 - another zone that has been difficult to control and slow to respond has improved.

When I went through the process of identifying the players and setting fixed APs I noticed a couple of things:

 - the badly behaving players announced themselves as “SonosZP” to the Deco app.  They are Play:1’s  The remaining players in my setup announced themselves just as “Sonos” or “Sonos Inc”, including another pair of Play: 1s.  So, clearly, all  Play: 1s are not created equal!

 - a couple of stereo pairs were routinely connected to two different APs.  Forcing them to connect to the same AP seems to have improved responsiveness.

I hope this is helpful to anyone else using a mesh wifi setup that experiences troublesome stereo pairs.

(I also hope that one day Sonos adds the intelligence to its players to make all this low-level network management an option rather than a necessity….).

The layer 2 network will see the hostname ‘SonosZP’ for all devices, the ‘Sonos’ or ‘Sonos Inc’ will be the vendor associated with the MAC prefix. I assume the Deco software is displaying the MAC vendor if it hasn't revolved the hostname. This is normal.